A variety of signaling modes can be used on communication links in memory systems. For example, advances in integrated-circuit technology for memory system components have led to changes in voltages and impedances on communication links between these memory system components. Unfortunately, providing a family of components, each of which supports a different one of these signaling modes for communication, is expensive and increases inventory requirements.
Moreover, it is often difficult to upgrade or change a particular combination of components in a memory system if the change involves modifying the signaling mode for communication between memory system components. This is because different signaling modes often have different common-mode voltages. These common-mode voltage differences may cause significant errors when attempting to determine driver and/or termination impedances in interface circuits that are associated with different signaling modes for communication.
Hence, what is needed are circuits and techniques which facilitate the use of different signaling modes in memory systems without the problems listed above.
Table 1 provides impedances and common-mode voltages associated with several signaling modes for communication.
Note that like reference numerals refer to corresponding parts throughout the drawings.